This invention relates to the preparation of macroglycols containing a controlled amount of carbonyl groups.
Polyisobutylene macroglycols are well known in the art and are generally produced by oxidizing a high molecular weight polymer and then obtaining complete reduction to hydroxyl functionality. See .alpha., .omega.-Glycols from Isobutylene and Some Derived Block Copolymers, Journal of Polymer Science: Part A, Vol. 2, pps. 5313-5318 (1961) E. B. Jones and C. S. Marvel. These conventional polyisobutylene macroglycols contain weight average hydroxyl functionality greater than 2 and thus are subject to gellation when reacted with diisocyanates in the preparation of segmented urethanes. This gellation occurs owing to the functionality distribution of the macroglycol which is determined by the distribution of off-chain unsaturation in the parent polymer. That is, if the parent polymer is an isobutylene-isoprene copolymer, the isoprene which is enchained 1,2 or 3,4, as opposed to 1,4 will produce side group functionality after ozonation of the high molecular weight material. The distribution of these side functional groups will be such that the higher the molecular weight molecule, the more functional groups attached thereto.
The use of conventional macroglycol production as discussed above, will therefore lead to a product in which all of the off-chain functionality is completely reduced to hydroxyl functionality or where incomplete reduction is performed there is no variation in completeness with molecular weight--a disadvantage for producing a soluble segmented urethane. The instant invention eliminates this problem by producing a macroglycol in which only a portion of the functionality is completely reduced to hydroxyl functionality, and molecules which would tend to have many hydroxyl groups are the ones selected for incomplete reduction, thus allowing for the production of soluble segmented urethane by subsequent reaction with diisocyanates.